Explosion-proof physician&#39;s lamp



July 3, 1962 H. s. RUBENS EXPLOSION-PROOF PHYSICIANS LAMP Filed June 4, 1959 FIG.

PIC-3.2

INVENTOR. HARRY S. RUBENS K11 mu a! c, (M

ATTORNEYS 3,642,797 EXPLGSEON-PROGF FHYSICIANS LAMP Harry S. Rubens, Massapequa, N.Y., assignor to Engelhard Hanovia, Inc, a corporation of New Jersey Filed June 4, 1959, Ser. No. 818,159 4 Claims. (Cl. 24059) that everything in the operating room be constructed so as to guard against the hazard of such ignition. The objection to the ordinary incandescent lamps employed in physicians or surgeons headlights results from the ever present possibility that the lamp bulb may break and the incandescent filament cause ignition of the anesthetic gas. The importance of the problem will be evident since accidents during operations seriously endanger the lives of human beings, and every single additional safety precaution represents significant progress I in the field.

It is therefore, the principal object of this invention to eliminate the danger of explosion caused by fracture of a light bulb in areas in which explosive gases are present in the atmosphere. More particularly, one object of this invention is to increase the safety in operating rooms where anesthetic gases may be ignited bycontact with the incandescent filament in surgeons headlights when the bulb is damaged.

As an illustrative example of one embodiment of the invention, an outer cylindrical metal envelope is mounted around an incandescent light bulb. The screw threaded connector of the bulb is sealed through the top of this cylindrical envelope. The bottom closure is for-med by a condensing lens, and the space between the bulb and the envelope is filled with a suitable non-inflammable transparent liquid. The metal envelope is advantageously made of a material such as aluminum or plated brass, which has good reflectivity to direct light toward the lens, and good heat conducting properties to avoid heat build-up within the casing.

In accordance with the invention, protection against ignition of explosive gases due to fracture of a light bulb in an area where such gases are present is achieved by providing a hermetically closed space around the bulb which space is delimited by the bulb and an outer envelope. Preferably, the zone contains a quneching liquid so that fracture of the evacuated lamp bulb will assure instant entry of fluid and cooling of the filament.

In accordance With one principal feature of the present invention, an explosion-proof lamp includes an envelope which hermetically encompasses the bulb to prevent ignition of explosive gases by contact with the incandescent filament in the event of damage to the glass envelope.

In an improved embodiment, and as an additional I feature of this invention, the space formed between the bulb and the envelope contains a non-inflammable liquid. In the event of fracture of the lamp bulb, which is partially evacuated, the surrounding fluid will instantly be drawn inside and quench the filament. As another feature of this invention, the assembly consisting essentially of a bulb and the envelope, preferably with a quenching liquid filling, is mounted and forms part of a headlight for physicians or surgeons. Headlights of this type include generally a headband to be worn by a person in the usual manner, the front portion being adapted to support a lamp-housing. A conventional socket in the ire rates Fatent and the volume of the liquid increases.

grooves 15 as described above.

aerate? Patented July 3, 1952 2 housing permits securing the bulb-envelope assembly in the housing.

The sealed unit may also include arrangements for expansion and contraction of the quenching liquid with heating by the lamp bulb. This may be in the form of a flexible diaphragm, or an air bubble in the liquid surrounding the bulb. An air bubble is a particularly convenient and inexpensive way of providing for the expansion and contraction of the liquid. Furthermore, for lamps to be used by a surgeon or physician with the lamp mounted to direct light downwardly on a patient, the air bubble does not interfere with the optical system of the lamp. V

Other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description and from the drawing, in which:

' FIGURE 1 is a sectional view of one embodiment of an explosion-proof bulb assembly according to the invention; and

FIGURE 2 is an isometric view of a physicians or 'surgeons headlight provided with the explosion-proo bulb assembly of FIGURE 1.

With reference to FIGURE 1, a conventional bulb 10 of the type generally used in physicians headlights or other applications, is hermetically enclosed in an outer cylindrical envelope 1-2. The envelope is suitably made of aluminum since this metal exhibits good heat conductivity andreflectivity. The top 14 of the envelope is provided with concentrically arranged grooves 16 and an aperture in the center to form a corrugated ring. Extending through the aperture, the base 18 of the bulb is hermetically sealed to top 14 along the circular line 20. This may be accomplished by soft soldering or by means of an appropriate adhesive, or by a rubber-like gasket.

Another, second opening in the metal envelope 12, suitably the cylinder bottom facing the top 14 and of the size of the cylinder diameter, is hermetically sealed :by a light-transmissive window. For most applications and particularly in the case of bulbs for physicians headlights, a condensing lens 22 forms the bottom closure for the envelope 12. In order to obtain a hermetically tight seal, a gasket or any conventional adhesive which is not oil-soluble may be used for securing the lens in the aperture of the envelope. By forming an enlarged end portion, a circular shoulder 24 is provided which serves as a seat for the lens. While the assembly so described constitutes a lamp which is explosion-proof to a large extent, it has been found advantageous to substantially fill the space between the bulb 10 and the envelope 12 with a liquid 26. Acting as a quenching agent, the liquid filling must necessarily be non-inflammable. Additionally, a low freezing point and a high boiling point are desirable. Good heat conductivity of the liquid is considered an advantage, since the filling liquid transmits heat from the bulb to the envelope from which it is dissipated. There is a great number of liquids that can be used and good results have been obtained with transparent silicone oil. Instead of the silicone il, nearly any other non-flammable transparent liquid may be employed.

In operation, heat produced by the bulb is accumulated In order to provide a flexible area in the wall of the envelope 12, to permit expansion of the fluid the top 14 is provided with Thereby aflexible diaphragm is formed which permits expansion of the enclosed liquid. I

The same result may be accomplished by'the inclusion of an air bubble 28 in the envelope. At asltop 14- and an air bubble 28 are shown, it is not neces- It will be apparent sary to use both in the same lamp. that one or the other is sufiicient, depending on the temperature characteristics and the intended use of the lamp 7 assembly. 3

FIGURE 2 illustrates a conventional physicians headlight equipped With the explosion-proof bulb-envelope assembly shown in FIGURE 1. Devices of this type generally include a headband 30 such as that of FIG- URE 2 or of any other similar structure. By means 7 of a longitudinal slot 32 in one end and a cooperating clamp'screw provided with a knob 34, the band may be adjusted to lit the head of the wearer. At a location to be worn at the forehead, the headband carries a universal joint 36"which adjustably supports a lamp housing 38. In the drawing, the housing is illustrated as being partly broken away to show the outer metal envelope 12 of the liquid-filled bulb-envelope assembly. with the lens 22 located in the opening of the housing 33. The conthe e'flect of the collimating lens 22. This efiect may be reduced by restricting the aperture of lens 22, by the use of an appropriate external reflector, or by using a bulb having a flat surface facing the lens 22. By suitable geometric arrangements of this type the dispersion efiects of the oil may be avoided and the optical properties of the oil may in some cases even be'used to advantage.

It will be obvious that many more modifications may be made Within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

Whatis claimed is: 1 V L'In an explosion-proof'lamp,an incandescent light 7 bulbprovided with a base cap, an outer cylindrical metal envelope hermetically encompassing said bulb to form a space therebetween and being supported exclusively by e the base, a non-inflammable transparent liquid enclosed in said space, said envelope being sealed at one side by I ,an annular, concentrically corrugated closure having said mounted at the other side of said envelope to form the other closure of said envelope.

2. In a physicians headlight, a headband having a lamp housing mounted thereon, an incandescent light bulb provided with a base cap' removably mounted in said housing, an outer cylindrical metal envelope hermetically encompassing said bulb to form a space therebetween and being supported exclusively by the base, a non-inflammable liquid enclosed in said space, said envelope being sealed at one side by an annular, concentrically corrugated closure having said base cap sealed therethrough, and a condensing lens mounted at'the other side of said envelope to form the other closure thereof.

3. An explosion-proof lamp comprising an incandescent li ht bulb having an electrically connecting base mounted thereon, a cylindrical metal envelope encompassing the bulb and forming a space therebetween, the walls of the envelope at one end thereof extending inwardly inrthe form of a concentrically corrugated closure, the base being hermetically sealed to the closure and extending outwardly of the envelope, the envelope being supported exclusively by the base, a condensing lens mounted at the other end of the envelope and hermetically closing the envelope and a non-inflammable liquid substantially filling the said space. 7

4. A *physicians headlamp comprising a head band, a

housing mounted on the head band, socket means in the housing, an explosion-proof lamp comprising an incandescent light bulb having an electrically connecting base mounted thereon, a cylindrical metal envelope encompassing the bulb and forming a space therebetween, the walls 'of the envelope at one end thereof extending inwardly in the form of a concentricallycorrugated closure,

- the base being hermeticallysealed to the closure and extending outwardly of the envelope, the envelope being supported exclusively by the base, a condensing lens mounted at the other end of the envelope and hermetically closingthe envelope, and a non-inflammable liquid substantially filling the said space, the envelope being mounted in said housing with the base'engaging the socket.

base cap sealed therethrough, and a condensing 'lens ReEerencesCited in the 'file of this patent UNITED STATES PATENTS Great Britain 'Mar. 29, 193 

